High Quality Content by WIKIPEDIA articles! The United Association of Journeymen and Apprentices of the Plumbing, Pipefitting and Sprinkler Fitting Industry of the United States and Canada, commonly known as the United Association (UA) is a trade union of journeymen and apprentices of the plumbing, pipefitting, and sprinkler fitting industry of the United States and Canada. The members fabricate, install and service piping systems.